1. Field of the Invention
The invention relates generally to the lighting of stadia, playing fields and similar areas and particularly to lighting fixtures intended for such lighting applications and which utilize reflective surfaces in combination with illumination sources to produce desired work plane illumination levels.
2. Description of the Prior Art
The field of sports lighting has evolved over time into a form of outdoor lighting having characteristics similar to outdoor area lighting yet peculiar to those requirements which come into play when lighting athletic playing fields. Uniformity of illuminance is of critical importance as is illumination level per se with these factors being joined by the everpresent need for optimum performance at the lowest possible cost. Advances in the art thus occur at least in part through development of luminaire configurations which effectively deliver a maximal amount of flux onto a playing area. In the sports light field in particular both vertical and horizontal illuminances must also be addressed as must illumination levels required for optimum video camera operation inter alia. Luminaire design also typically takes into account conventional arrangements of pole locations, mounting heights and aiming angles. Other objectives include consistent overlap of beam patterns in order to maximize system performance while minimizing costly applications engineering efforts usually associated with sports lighting systems. The prior art has long encompassed the mounting of discrete clusters of sportslighting luminaires at periodic locations about the perimeter of a playing area. Within these conventional system constraints, luminaire performance is evaluated not only as a single unit but also within these discrete clusters, the net distribution of each cluster being necessarily considered in performance evaluation. As is therefore to be appreciated, luminaire design in the sportslighting field is a complex matter dependent upon a variety of factors not the least of which is total system cost.
When considering cost, operational costs cannot be dismissed as inconsequential. Prior sportslighting systems which utilize less efficient light sources such as incandescent and mercury vapor must be improved in order to gain the benefits of greater efficiency with comparable light levels and desirable light quality which are to be gained from sources such as high pressure sodium and metal halide, as example Greatest luminaire flexibility is attained through luminaire design capable of using the widest variety of illumination sources to include high pressure sodium and metal halide and the like.
Examples of prior art lighting designed for the purposes to which the present invention are directed are disclosed by Lemons et al in U.S. Pat. Nos. 4,864,476 and 5,313,379 and by Tickner in U.S. Pat. Nos. 5,355,290 and 5,377,086. As is conventional in the art, these patents disclose the use of reflector structures intended to provide desired illumination levels on a work plane. Sportslighting luminaires of the prior art can also be seen in the TV Sportslighting luminaire manufactured by Lithonia Lighting, a division of National Service Industries, Inc. of Atlanta, Ga., this luminaire including in its optical structure an anodized aluminum reflector capable of a range of beam spreads. The TV luminaire further includes a horizontal degree aiming scale and repositioning locator as well as a vertical aiming adjustment mechanism complete with degree aiming scale and a repositioning stop. While sportslighting luminaire devices such as the TV luminaire of Lithonia Lighting provide lighting capabilities of substantial utility and while other luminaire devices of the prior art also provide capabilities desirably useful in the sportslighting field, a need exists in the art for sportslighting luminaires capable of improved cost and energy efficiencies and which particularly provide performance capabilities allowing use of fewer luminaires within a given system arrangement.